Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2010
Publication Date: 9/30/2010
Citation: Meyer, S.L., Halbrendt, J.M., Carta, L.K., Skantar, A.M., Liu, T., Abdelnabby, H.M., Vinyard, B.T. 2010. Toxicity of 2,4-diacetylphloroglucinol (DAPG) to plant-parasitic and bacterial-feeding Nematodes. Journal of Nematology. 41(4):274-280. Interpretive Summary: Plant-parasitic nematodes are microscopic worms that cause ten billion dollars in U.S. crop losses annually. A major problem facing growers is the lack of safe and effective methods for reducing crop losses caused by nematodes. Scientists are looking at beneficial bacteria as potential biocontrol agents for managing plant-parasitic nematodes. Some of the bacteria that suppress plant diseases caused by fungi are known to produce an antibiotic called DAPG. In this study, DAPG was tested to see if it is toxic to plant-parasitic nematodes and to beneficial nematodes that feed upon bacteria. DAPG was toxic to two out of four tested species of plant-parasitic nematodes, but was not toxic to the three bacterial-feeding nematodes that were tested. The results are significant because they indicate that this natural compound has potential for use in reducing populations of some plant-parasitic nematodes without affecting beneficial bacteria-feeding nematodes. This research will be used by scientists developing environmentally safe methods for managing diseases caused by nematodes.
Technical Abstract: The antibiotic 2,4-diacetylphloroglucinol (DAPG) is produced by some isolates of the beneficial bacterium Pseudomonas fluorescens. DAPG is toxic to many organisms, and crop yield increases have been reported after application of DAPG-producing P. fluorescens. This study was conducted to determine whether DAPG is toxic to selected nematodes. The plant-parasitic nematodes Heterodera glycines, Meloidogyne incognita, Pratylenchus scribneri and Xiphinema americanum, and the bacterial-feeding nematodes Caenorhabditis elegans, Pristionchus pacificus, and Rhabditis rainai, were immersed in concentrations ranging from 0 to 100 micrograms/ml DAPG. Egg hatch and viability of juveniles and adults were determined. DAPG was toxic to X. americanum adults, with an LD50 of 8.3 micrograms/ml DAPG. DAPG decreased M. incognita egg hatch, but stimulated C. elegans hatch during the first hours of incubation. Viability of M. incognita J2 and of C. elegans J1 and adults was not affected. There were no observed effects on the other nematodes. The study indicated that DAPG is not toxic to all nematodes, and did not affect the tested species of beneficial bacterial-feeding nematodes. Augmentation of DAPG-producing P. fluorescens populations for nematode biocontrol could be targeted to specific nematode species known to be affected by the compound, or the bacteria could be used for other possible effects against nematodes and other pathogens, such as induced plant resistance.